Basic to all research on anaerobic bacteria and their relationship to human infection and human health is the accurate recognition and identification of anaerobes in clinical specimens and the body cavities of man. Nearly all modern work on anaerobic bacteria cites and uses procedures and information that have been developed in the V.P.I. Anaerobic Bacteriological Research Program (GMS 14604). The most common problem organisms of clinical infections can now be recognized with accuracy if our procedures are followed. Recognition is essential for relating an isolate or a species to the body of knowledge concerning the properties and potential significance of that species. However, the information we have developed probably covers only about 10 per cent of the kinds of anaerobes of direct significance to human health. Lack of recognition by clinical and research laboratories of the additional types we know to be present is a major deterrent to progress in this field. The major objectives of this basic research program in anaerobic bacteriology are the determination of differential properties, metabolic characteristics, and nutritional requirements of anaerobic bacteria; correlation of phenotypes with DNA/DNA homology groups (which represents the most advanced scientific basis for recognition of distinct specific entities); studies of the infectious and antigenic properties and their relationships to therapy and host defenses; determination of the relationship of anaerobes to bile, cholesterol, or tissue degradation; and basic characterization and description of the organisms. The basic research information we develop on anaerobic bacteria is finding immediate application in infectious disease, cancer, cholesterol metabolism and heart disease, burn and trauma infections, nutrition, organ transplants, pediatrics, dentistry, food preservation and poisoning, venereal disease, enzymology, and cellular analysis.